Actually...getting sprites isn't Nintendo related, they're just licensing the games from the creators: GAMEFREAK.
Though that doesn't matter.
You just need to run the game emulator and save the images of the sprites. Not too hard.
Or just rip them from other sites? They can't legally claim them as theirs since GAMEFREAK owns the sprites and, modded or otherwise, the base work is legal property of GAMEFREAK. (Who has done nothing objecting to fan work/fan bases)
Just a cold way to look at it, I mean we could have people go in and rip/save sprites by hand, though that'll take a while too.

The knowledge part... That is a good idea, though to be honest, it'll be hard to beat bulbapedia...Still, offering an alternative never hurts.

Videos...
A lot of people who make videos would rather the site have a section with links to detailed walkthroughs and stuff, rather than it all being on the main site's channel. Just my two cents, especially since a lot of people like money and they make money off their videos. Plus they'd prefer subscribers go to them. I say feature the LPs of those who are loyal to the site. Like... Loyal loyal. They'll gain subs, but redirect that same traffic to the site and vice-versa. A symbiotic growth! (Insert infinity sign) That way the site attracts people to the walk through videos, and the walk-through videos attract people to the site.

Just my two cents o.o Sorry if I seem like a know it all, I certainly am not. I'm pretty dumb xD So uhm, maybe this is all just dumb and I should be ignored on this topic. Sorry to bother ya folks o.o;;;